Fuel reformer and manufacturing method of the same

ABSTRACT

The present invention concerns a fuel reformer for reforming a hydrocarbon base fuel in to a hydrogen rich gas and a manufacturing method thereof, and the fuel reformer of the present invention wherein a Cr oxide layer is formed on at least a part of the surface of steel material making the reformer produces no red scale through water vapor oxidation of the surface of steel material making the reformer, even when exposed to an atmosphere of low oxygen concentration and/or high water vapor concentration under a high temperature and has an extremely important industrial utility value because it is highly heat resistant, light, low cost and cheap, highly reliable and long life, and moreover a cheap, highly reliable and long life fuel reformer can be manufactured at a low cost and easily by the manufacturing method of the present invention.

FIELD OF THE INVENTION

The present invention concerns a fuel reformer and a manufacturingmethod thereof, and more particularly, a fuel reformer for reforming ahydrocarbon base fuel into a hydrogen rich gas and a manufacturingmethod thereof.

BACKGROUND ART

In case of supplying a reformer with a hydrocarbon base fuel, forexample a mixture gas of methane and water vapor [for example,steam/carbon (mole ratio)=about 2.5] and reforming the same into ahydrogen rich gas (endothermic reaction) through water vapor reforming,the operating temperature of the reformer is approximately 700° C. (exittemperature of reforming catalyst layer); but, the surface temperatureof the material making the reformer is supposed to be equal or superiorto about 1000° C. in the vicinity of the heating portion of thereformer.

There has been a problem that the surface of steel material making thereformer, exposed to an atmosphere of low oxygen concentration and/orhigh water vapor concentration under a high temperature, is oxidized bywater vapor, a rough, porous and fragile iron oxide layer (supposed tocontain Fe₂O₃ mainly) (referred to as red scale, hereinafter) is formedon the surface thereof, the red scale tends to progress on and on intothe substrate, having a nature of peeling off easily from the substrate,and the more the red scale peels off from the substrate, the more thecorrosion of steel material advances. Though the destruction of thematerial by corrosion may be mitigated by increasing the thickness ofthe steel material, the weight increases, the processing becomesdifficult and the cost increases.

The conventional fuel reformer has been used a heat resistant alloyUSUS310S or the like) or super alloy (Incoloy800 or the like) of Cr:20mass %, Ni:18 mass % or more. However, even in a reformer made of superalloy, for instance, red scale appeared on the surface of the combustiongas passage side including the heating portion.

A fuel reformer material containing C 0.1 wt % or less, Ni 8 to 29 wt %,Nb 0.1 to 0.4 wt %, containing one or two elements chosen from Ti, Zr by0.05 to 0.3 wt %, and further containing N 0.02 to 0.05 wt %, B 0.003 to0.01 wt % and composed of remaining Fe and inevitable impurities (JapanPatent Publication Laid-Open HEI 5-339679); however, a problem of thegeneration of red scale was not considered.

The object of the present invention is to provide a light, low cost andcheap, highly reliable and long life fuel reformer, that resolvesconventional problems, and produces no red scale through water vaporoxidation of the surface of steel material making the reformer, evenwhen exposed to an atmosphere of low oxygen concentration and/or highwater vapor concentration under a high temperature.

DISCLOSURE OF THE INVENTION

In order to solve the aforementioned problems, the fuel reformeraccording to claim 1 is a fuel reformer for reforming a hydrocarbon basefuel into a hydrogen rich gas, wherein Cr oxide layer is formed on atleast a part of the surface of steel material making the reformer.

The fuel reformer of claim 2 is characterized by that, in the fuelreformer of claim 1, the Cr oxide layer is formed on a surface of a fuelcombustion gas passage side.

The fuel reformer of claim 3 is characterized by that, in the fuelreformer of claim 1, the Cr oxide layer is formed on a surface of amixture gas passage from a fuel supply portion for supplying thereformer with mixture gas of raw fuel for reforming and water vapor to areform catalyst filled portion.

The fuel reformer of claim 4 is characterized by that, in the fuelreformer of claim 1, wherein the Cr oxide layer is formed on a surfaceof the fuel combustion gas passage side and also on the surface of themixture gas passage from a fuel supply portion for supplying thereformer with mixture gas of raw fuel for reforming and water vapor tothe reforming catalyst filled portion.

The fuel reformer of claim 5 is characterized by that, in the fuelreformer of any of claims 1 to 4, the average thickness of the Cr oxidelayer is 5 to 100 μm.

The fuel reformer of claim 6 is characterized by that, in the fuelreformer of any of claims 1 to 5, a thin film having a Cr concentrationhigher than a Cr concentration of a base material is formed on a surfaceof steel material making the reformer, and thereafter a Cr oxide layerformed by heat treatment is formed thereon.

The claim 7 is a manufacturing method of a fuel reformer comprising thesteps of; forming a Cr oxide layer on a surface of raw steel materialthrough a heat treatment of raw steel material in an oxidizingatmosphere of 600 to 1000° C., and manufacturing the reformer using rawsteel material where the Cr oxide layer is formed thereon.

The claim 8 is a manufacturing method of a fuel reformer comprising astep of forming a Cr oxide layer on a surface of raw steel material,through a heat treatment of the fuel reformer made of raw steel materialin an oxidizing atmosphere of 600 to 1000° C.

The claim 9 is a manufacturing method of a fuel reformer comprising thesteps of; forming a thin film having a Cr concentration higher than a Crconcentration of a base material on a surface of raw steel material, andthereafter forming a Cr oxide layer on the surface of raw steelmaterial, through a heat treatment in an oxidizing atmosphere of 350 to650° C., and manufacturing the reformer using raw steel material onwhich the Cr oxide layer is formed thereon.

The claim 10 is a manufacturing method of a fuel reformer comprising thesteps of; forming a thin film having a Cr concentration higher than a Crconcentration of a base material on a surface of raw steel material, andthereafter forming a Cr oxide layer on the surface of raw steelmaterial, through a heat treatment of a fuel reformer made of raw steelmaterial in an oxidizing atmosphere of 350 to 650° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a cross-portional illustrative drawing of an embodiment of thefuel reformer of the present invention;

FIG. 2 a cross-portional illustrative drawing of another embodiment ofthe fuel reformer of the present invention; and

FIG. 3 is a cross-portional illustrative drawing of another embodimentof the fuel reformer of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to a fuel reformer of claim 1 of the present invention, a Croxide layer is formed on at least a part of the surface of steelmaterial making the fuel reformer. The Cr oxide layer is specifically aspinel oxide layer of Cr mainly FeO.Cr₂O₃ or Cr₂O₃, dense and excellentin close adhesion with the substrate steel material, having few latticedefect, reducing remarkably diffusion of metal ion and oxygen ion, andbeing able to prevent water vapor oxidation. Consequently, theproduction of red scale is suppressed, the heat resistance is improved,whereby the life and reliability of the fuel reformer are improved.

Preferably, the average thickness of the Cr oxide layer is in a range of5 to 100 •. A Cr oxide layer having an average thickness of 5 to 100 •is good in adherence to the substrate steel material, dense, andexcellent in water vapor oxidation resistance. If it is less than 5 •,points where Cr oxide layer is partially absent appear, a uniform anddense Cr oxide layer might not be formed, while if it exceed 100 •, ittakes long time to form the Cr oxide layer and becomes uneconomic.

According to the fuel reformer of claim 6, a thin film (thin film ofchromium alloy, thin film of chromium, or the like. Average thickness onthe order of about 1 to 100 •) having a Cr concentration higher than aCr concentration of a base material is formed preliminarily on thesurface of steel material making the reformer by chromizing, chromiumplating or other methods, and thereafter a Cr oxide layer is formed byheat treatment. By so doing, it becomes less troublesome because theheat treatment temperature can be reduced, energy quantity can belowered allowing to reduce energy consumption. Moreover, the Cr oxidelayer formed by heat treatment becomes dense. In addition, as a thinfilm having a Cr concentration higher than a Cr concentration of a basematerial is formed preliminarily on the surface of steel material makingthe reformer, a dense Cr oxide layer can be formed in a short period oftime on the surface, even when the base material Cr concentration islow.

According to the fuel reformer of claim 7, a Cr oxide layer is formed onthe surface of raw steel material, through a heat treatment of raw steelmaterial in an oxidizing atmosphere of 600 to 1000° C., and the fuelreformer is manufactured using raw steel material where the Cr oxidelayer is formed thereon.

A spinel oxide layer of Cr containing mainly FeO.Cr₂O₃ or Cr₂O₃ can beformed on the surface of raw steel material, through a heat treatment ofraw steel material in the oxidizing atmosphere of 600 to 1000° C.,preferably for 30 min to 10 hours as mentioned above.

Consequently, the fuel reformer can be manufactured by forming the Croxide layer on the surface of raw steel material and thereafter,assembling or welding such steel material.

It should be appreciated that if the heat treatment temperature of rawsteel material is less than 600° C., the Cr oxide layer might not beformed, while if it exceeds 1000° C., an expensive heater will berequired, increasing the energy quantity to be input into the heater,and making the treatment uneconomic; so it is preferably in atemperature range of 600 to 1000° C. Moreover, if the heat treatmenttime is less than 30 min, an uniform and dense Cr oxide layer might notbe formed, while if it exceeds 10 hours, the energy quantity to be inputincreases, making the treatment uneconomic. Therefore, the heattreatment time is preferably in a time range of 30 min to 10 hours.

Beside, according to the fuel reformer of claim 8, a Cr oxide layer isformed on the surface of raw steel material, through a heat treatment ofa fuel reformer itself made of raw steel material in an oxidizingatmosphere of 600 to 1000° C. Thus, a spinel oxide layer of Crcontaining mainly FeO.Cr₂O₃ or Cr₂O₃ can be formed on the surface of rawsteel material, through a heat treatment of the fuel reformer itself inthe oxidizing atmosphere of 600 to 1000° C., preferably for 30 mins to10 hours.

Consequently, a fuel reformer having a long life and an improvedreliability can also be manufactured by the invention according to thepresent claim.

According to the fuel reformer of claim 9, a Cr oxide layer is formed onthe surface of raw steel material by chromizing or chrome plating or theother methods, through a heat treatment in an oxidizing atmosphere of350 to 650° C., after forming a thin film (thin film of chromium alloy,thin film of chromium, or the like. Average thickness on the order ofabout 1 to 100 •) having a Cr concentration higher than a Crconcentration of a base material on the surface of raw steel materialand, the fuel reformer is made of raw steel material on which thesurface the Cr oxide layer is formed. It becomes less troublesomebecause the heat treatment is performed in the oxidizing atmosphere of350 to 650° C., energy quantity can be lowered allowing to reduce energyconsumption. Moreover, the Cr oxide layer formed by heat treatmentbecomes dense. In addition, since a thin film having a Cr concentrationhigher than a Cr concentration of a base material is formedpreliminarily on the surface of steel material making the reformer, adense Cr oxide layer can be formed in a short period of time on thesurface thereof, even when the base material Cr concentration is low.

A fuel reformer can be manufactured by forming a thin film having a Crconcentration higher than a Cr concentration of a base material on thesurface of raw steel material, and thereafter forming a Cr oxide layer,through a heat treatment in an oxidizing atmosphere of 350 to 650° C.,and assembling or welding such steel material. The heat treatmenttemperature is 350 to 650° C., and if it is less than 350° C., the Croxide layer might not be formed, while if it exceeds 600° C., the energyquantity also increases, making it uneconomic in respect to the effect.

According to the fuel reformer of claim 10, a thin film (thin film ofchromium alloy, thin film of chromium, or the like. Average thickness onthe order of about 1 to 100 •) having a Cr concentration higher than aCr concentration of a base material is formed on the surface of rawsteel material, and thereafter a Cr oxide layer is formed on raw steelmaterial, through a heat treatment of a fuel reformer made of raw steelmaterial in an oxidizing atmosphere of 350 to 650° C. It becomes lesstroublesome because the heat treatment is performed in the oxidizingatmosphere of 350 to 650° C., energy quantity can be lowered allowing toreduce energy consumption, and moreover, the Cr oxide layer formed byheat treatment becomes dense. In addition, since the thin film having aCr concentration higher than a Cr concentration of a base material isformed preliminarily on the surface of steel material making thereformer, a dense Cr oxide layer can be formed in a short period of timeon the surface thereof, even when the base material Cr concentration islow. The treatment temperature is 350 to 650° C., and if it is less than350° C., the Cr oxide layer might not be formed, while if it exceeds600° C., the energy quantity also increases, making it uneconomic inrespect to the effect.

Consequently, a fuel reformer having a long life and an improvedreliability can also be manufactured by the invention according to thepresent claim.

Now embodiments of the present invention will be described referring tothe drawings.

FIG. 1 is a cross-portional illustrative drawing of an embodiment of afuel reformer of the present invention.

In FIG. 1, a fuel reformer 1A of the present invention comprises areforming tube outer cylinder 2, a reforming tube inner cylinder 3, areforming tube inner cylinder upper plate 4, a reforming tube innercylinder lower plate 5, a raw fuel inlet 6 provided on the reformingtube inner cylinder lower plate 5, a reformed gas outlet 7 or others,and also comprises a reforming tube 9 provided with a heating portion 8for introducing a fuel gas for heating into a hollow portion installedat the middle thereof, a catalyst tube 10 fitted to the inside of thereforming tube 9, a reforming catalyst 11 (for instance, Ni, rutheniumcatalyst supported by aluminum, or the like) filled between thereforming tube inner cylinder 3 and the catalyst tube 10 and alsoarranged on the reforming tube inner cylinder upper plate 4, acombustion exhaust gas pipe 13 for directing the combustion exhaust gasby bringing into contact with the outside of the reforming tube 9, andthereafter discharging outside from a combustion exhaust gas outlet 12,a combustion gas pipe 14 extending and inserted in order to introducecombustion gas into the heating portion 8, a burner 15 installed belowthe combustion gas pipe 14 for burning combustion gas, and others.

In FIG. 1, gas fuel is burned by introducing gas fuel and air into theburner 15, and combustion gas is directed to the heating portion 8through the combustion gas pipe 14 as shown by the broken line arrow forheating the reforming catalyst 11, then, combustion exhaust gas isdischarged from the combustion exhaust gas outlet 12 passing between thereforming tube outer cylinder 2 and the combustion exhaust gas pipe 13.On the other hand, a hydrocarbon base fuel, for instance, methane isintroduced with water vapor from the raw material inlet 6 into the fuelreformer 1A as shown by arrow, brought into contact with the heatedreforming catalyst 11, and reformed. The operating temperature of thefuel reformer 1A is controlled to about 700° C. (outlet temperature ofthe reforming catalyst 11) and operated. The produced reformed gas (if araw material of steam/carbon (mole ratio)=about 2.5, a reformed gascontaining hydrogen by about 75%, carbon monoxide by about 10 andseveral %, carbon dioxide by the order of 10 and several %, and methanegas for the remainder) is discharged from the reformed gas outlet 7passing between the reforming tube outer cylinder 2 and the catalysttube 10 as shown by the arrow.

In FIG. 1, a Cr oxide layer is formed on the surface of steel materialmaking the fuel reformer 1A comprising the combustion gas pipe 14, thecombustion exhaust gas pipe 13, the combustion exhaust gas outlet 12,the reforming tube outer cylinder 2, the reforming tube inner cylinder3, the reforming tube inner cylinder upper plate 4 and others at theside where combustion gas flows by coming into contact with the pointsshown by bold lines, by the heat treatment of raw steel material in anoxidizing atmosphere of 600 to 1000° C. for 30 min to 10 hours.

The side where combustion gas flows by coming into contact with thepoints shown by the bold line including the heating portion 8 of thefuel reformer 1A is in a hot and low oxygen concentration atmosphereeasy to provoke the water vapor oxidation. However, as the Cr oxidelayer is formed preliminarily on these surfaces of the combustion gaspassage side, the water vapor oxidation on the surface is prevented andthe generation of red scale is prevented, improving the heat resistance.Thereby, the life and reliability of the reformer are improved.

FIG. 2 is a cross-portional illustrative drawing of another embodimentof a fuel reformer of the present invention.

In FIG. 2, a fuel reformer 1B of the present invention is similar to thefuel reformer 1A shown in FIG. 1, except that the Cr oxide layer isformed preliminarily on a reforming tube outer cylinder upper plate 5, araw fuel inlet 6, a part of the upper part of a catalyst tube 10 orothers shown by the bold line, in short, on the surface of the passage,where a mixture gas flows and comes into contact therewith, from a fuelsupply portion for supplying the mixture gas of raw fuel for reformingand water vapor to a filled portion of the reforming catalyst 11.

The mixture gas passage from the fuel supply portion for supplying thefuel reformer 1B with the mixture gas to a filled portion of thereforming catalyst 11 is in a hot and high water vapor concentrationatmosphere easy to provoke the water vapor oxidation. However, since theCr oxide layer is formed on the surface of the mixture gas passage, thewater vapor oxidation on the surface and the generation of red scale areprevented, improving the heat resistance. Thereby, the life andreliability of the reformer are improved.

FIG. 3 is a cross-portional illustrative drawing of another embodimentof the fuel reformer of the present invention.

In FIG. 3, a fuel reformer 1C of the present invention is similar to thefuel reformers 1A, 1B shown in FIG. 1 or FIG. 2, except that a Cr oxidelayer is formed on the surface of steel material making the fuelreformer 1C comprising a combustion gas pipe 14, a combustion exhaustgas pipe 13, a combustion exhaust gas outlet 12, a reforming tube outercylinder 2, a reforming tube inner cylinder 3, reforming tube innercylinder upper plate 4 and the others at the side where combustion gasflows coming into contact with the points shown by bold lines and alsothe Cr oxide layer is formed on the reforming tube outer cylinder upperplate 5, the raw fuel inlet 6, a part of the upper part of the catalysttube 10 or the others shown by the bold line, in short, on the surfaceof the mixture gas passage from the fuel supply portion for supplyingthe mixture gas of raw fuel for reforming and water vapor to the filledportion of the reforming catalyst 11.

Since the combustion gas passage side including the heating portion 8 ofthe fuel reformer 1C is in a hot and low oxygen concentration atmosphereeasy to provoke the water vapor oxidation, and the mixture gas passagefrom the fuel supply portion for supplying the fuel reformer 1C withmixture gas to a filled portion of the reforming catalyst 11 is in a hotand high water vapor concentration atmosphere easy to provoke the watervapor oxidation, the formation of the Cr oxide layer on the surface ofthe combustion gas passage side and the surface of the mixture gaspassage prevents the water vapor oxidation on both surfaces and preventsthe generation of red scale, improving the heat resistance. Thereby, thelife and reliability of the reformer are improved.

The description of the aforementioned embodiments is only for thepurpose of explanation of the present invention and does not limit theinvention described in claims, nor reduce the scope. Moreover, thecomposition of respective parts of the present invention is not limitedto the aforementioned embodiments, but various variants can be madewithout departing from the technical scope described in claims.

In short, the fuel reformer of the present invention is not limited tothe fuel reformers of the type described in FIG. 1 to FIG. 3, but it mayalso be, for example, a multi-tube type fuel reformer, a flat plate typefuel reformer or the like, and as other examples, more particularly,fuel reformers described in FIG. 1 and FIG. 3 of Japanese PatentPublication No. 2703831, fuel reformers described in FIG. 2 to FIG. 8 ofJapan Patent Application Laid-Open Hei 6-13096, fuel reformers describedin FIG. 1 to FIG. 3 of Japan Patent Application Laid-Open Hei 6-56401,fuel reformers described in FIG. 1, FIG. 4 and FIG. 7 of Japan PatientApplication Laid-Open Hei 7-109105, fuel reformers described in FIG. 1and FIG. 3 of Japan Patent Application Laid-Open Hei 7-223801, a fuelreformer described in FIG. 1 of Japan Patent Application Laid-Open Hei7-335238, fuel reformers described in FIG. 1 and FIG. 3 of Japan PatentApplication Laid-Open Hei 9-241002, fuel reformers described in FIG. 1of Japan Patent Application Laid-Open Hei 9-306553, fuel reformersdescribed in FIG. 1 to FIG. 4 of Japan Patent Application Laid-Open Hei10-125342 and others can be cited.

Since the fuel reformer of claim 1 of the present invention does notincrease the thickness of the reformer of the prior art, and a Cr oxidelayer is formed preliminarily at least on a part of the surface of steelmaterial making the reformer, it has a remarkable effect of providing aheat resistive, light, low cost and cheap, highly reliable and long lifefuel reformer, that produces no red scale through water vapor oxidationof the surface of steel material making the reformer, even when exposedto an atmosphere of low oxygen concentration and/or high water vaporconcentration under a high temperature.

In the fuel reformer of claim 2 of the present invention, as the Croxide layer is formed preliminarily on the surface of the combustionpassage side of steel material, where water vapor oxidation is producedeasily under a high temperature and a low oxygen concentration, therebyit has remarkable effects of preventing water vapor on the surface,preventing production of red scale, improving the heat resistance, andbeing light, low cost and cheap, highly reliable and long life.

For the fuel reformer of claim 3 of the present invention, as the Croxide layer is formed preliminarily on the surface of the mixture gaspassage from the fuel supply portion for supplying the mixture gas tothe filled portion of the reforming catalyst, where water vaporoxidation is produced easily under a high temperature and a high watervapor concentration, it has remarkable effects of preventing water vaporoxidation on the surface, preventing production of red scale, improvingthe heat resistance, and being light, low cost and cheap, highlyreliable and long life.

For the fuel reformer of claim 4 of the present invention, the Cr oxidelayer is formed preliminarily on any of the surface of the combustionpassage side where water vapor oxidation is produced easily under a hightemperature and a low oxygen concentration, and the surface of themixture gas passage from the fuel supply portion for supplying mixturegas to the filled portion of the reforming catalyst in an atmospherewhere water vapor oxidation is produced easily under a high temperatureand a high water vapor concentration, thereby it has remarkable effectsof preventing water vapor oxidation on the surface, preventingproduction of red scale, improving the heat resistance, and being light,low cost and cheap, highly reliable and long life.

For the fuel reformer of claim 5 of the present invention, since theaverage thickness of the Cr oxide layer is 5 to 100 μm, the Cr oxidelayer has remarkable effects of having a good adhesion to the surface ofthe substrate steel material and an excellent resistance to the watervapor oxidation.

According to the fuel reformer of claim 6 of the present invention,since a thin film having a Cr concentration higher than a Crconcentration of a base material is formed preliminarily on the surfaceof steel material making the reformer by a method such as chromizing orchrome plating, and thereafter a Cr oxide layer is formed by heattreatment, the heat treatment temperature can be reduced, energyquantity can be lowered allowing to reduce energy consumption, andmoreover, the Cr oxide layer formed by heat treatment becomes dense.Furthermore, since a thin film having a Cr concentration higher than aCr concentration of a base material is formed preliminarily on thesurface of steel material making the reformer, it has a remarkableeffect capable of forming a dense Cr oxide layer in a short period oftime on the surface thereof, even when the base material Crconcentration is low.

The manufacturing method of claim 7 has a remarkable effect capable offorming easily the Cr oxide layer on the surface of raw steel materialbefore manufacturing the fuel reformer of the present invention, to formthe Cr oxide layer on the surface of raw steel material and then tomanufacture easily the fuel reformer of the present invention byassembling or welding, using the same.

The manufacturing method of claim 8 of the present invention has aremarkable effect capable of manufacturing the fuel reformer of thepresent invention, by forming the Cr oxide layer on the surface of rawsteel material, through the treatment of a fuel reformer made of rawsteel material where the Cr oxide layer is not formed yet.

For the manufacturing method of claim 9 of the present invention, sincea thin film having a Cr concentration higher than a Cr concentration ofa base material is formed on the surface of raw steel material, andthereafter a Cr oxide layer is formed by a heat treatment in anoxidizing atmosphere of 350 to 650° C., and then the fuel reformer ismanufactured using the raw steel material where the Cr oxide layer isformed, it becomes less troublesome, energy quantity can be loweredallowing to reduce energy consumption, thereby the Cr oxide layer formedby heat treatment becomes dense. Moreover, since a thin film having a Crconcentration higher than a Cr concentration of a base material isformed preliminarily on the surface of steel material making thereformer, a dense Cr oxide layer can be formed in a short period of timeon the surface thereof, even when the base material Cr concentration islow.

According to the manufacturing method of claim 10 of the presentinvention, a thin film having a Cr concentration higher than a Crconcentration of a base material is formed on the surface of raw steelmaterial thereof, and thereafter a Cr oxide layer is formed on raw steelmaterial, through a heat treatment of a fuel reformer made of raw steelmaterial in an oxidizing atmosphere of 350 to 650° C., so it becomesless troublesome, energy quantity can be lowered allowing to reduceenergy consumption, and also the Cr oxide layer formed by heat treatmentbecomes dense. In addition, the thin film having a Cr concentrationhigher than a Cr concentration of a base material is formedpreliminarily on the surface of steel material making the reformer, soit has a remarkable effect capable of forming a dense Cr oxide layer ina short period of time on the surface thereof, even when the basematerial Cr concentration is low.

INDUSTRIAL APPLICABILITY

The present invention concerns a fuel reformer for reforming ahydrocarbon base fuel into a hydrogen rich gas and a manufacturingmethod thereof and the fuel reformer of the present invention producesno red scale through water vapor oxidation of the surface of steelmaterial making the reformer, even when exposed to an atmosphere of lowoxygen concentration and/or high water vapor concentration under a hightemperature. The fuel reformer of the present invention has an extremelyimportant industrial utility value because it is highly heat resistant,light, low cost and cheap, highly reliable and long life, and moreover acheap, highly reliable and long life fuel reformer can be manufacturedat a low cost and easily by the manufacturing method of the presentinvention.

1. A fuel reformer vessel for reforming a hydrocarbon base fuel andwater into a hydrogen rich gas comprising a reformer catalyst filledportion, wherein a Cr oxide layer is formed on at least a part of asurface of a steel material, wherein said fuel reformer vessel is formedof a material comprising the steel material, and said surface of thesteel material is under an oxidative atmosphere by water vapor.
 2. Thefuel reformer vessel of claim 1, wherein said Cr oxide layer is formedon a surface of a fuel combustion gas passage side thereof.
 3. The fuelreformer vessel of claim 1, wherein said Cr oxide layer is formed on asurface of a mixture gas passage from a fuel supply portion forsupplying the fuel reformer vessel with mixture gas of raw fuel andwater for reforming to the reforming catalyst filled portion thereof. 4.The fuel reformer vessel of claim 1, wherein said Cr oxide layer isformed on a surface of a fuel combustion gas passage side thereof and onthe surface of the mixture gas passage from a fuel supply portion forsupplying the fuel reformer vessel with mixture gas of raw fuel andwater vapor for reforming to the reforming catalyst filled portionthereof.
 5. The fuel reformer vessel of claim 1, wherein an averagethickness of said Cr oxide layer is 5 to 100 μm.
 6. The fuel reformervessel of claim 1, wherein said Cr oxide layer is formed on said surfaceof the steel material by heat treating the fuel reformer vessel under anoxidizing atmosphere thereby to convert Cr to Cr oxide after formingthereon a thin film containing Cr in a higher concentration than that ofa base material thereof.
 7. A method of manufacturing a fuel reformervessel for reforming a hydrocarbon base fuel and water into a hydrogenrich gas, the fuel reformer vessel comprising a reformer catalyst filledportion, said method comprising the steps of: forming a Cr oxide layeron at least a part of a surface of raw steel material by heat treatingsaid raw steel material under an oxidizing atmosphere of 600 to 1000°C., said surface of the steel material is under an oxidative atmosphereby water vapor; manufacturing a vessel for the fuel reformer vessel byusing said raw steel material on which the Cr oxide layer is thusformed; and filling thus manufactured vessel with a reforming catalystthereby to produce the fuel reformer vessel.
 8. A method ofmanufacturing a fuel reformer vessel for reforming a hydrocarbon basefuel and water into a hydrogen rich gas, the fuel reformer vesselcomprising a reformer catalyst filled portion, said method comprisingthe steps of: manufacturing a vessel for the fuel reformer vessel byusing raw steel material; forming a Cr oxide layer on at least a part ofa surface of the raw steel material by heat treating in an oxidizingatmosphere of 600 to 10000° C., said surface of the steel material isunder an oxidative atmosphere by water vapor; and filling said vesselwith a reforming catalyst thereby to produce the fuel reformer vessel.9. A method of manufacturing a fuel reformer vessel for reforming ahydrocarbon base fuel and water into a hydrogen rich gas, the fuelreformer vessel comprising a reformer catalyst filled portion, saidmethod comprising the steps of: forming a Cr oxide layer on at least apart of a surface of a steel material for making a fuel reformer vesselby heat treatment of 350 to 650° C. under an oxidizing atmosphere toconvert Cr to Cr oxide after forming thereon a thin film containing Crin a higher concentration than that of a base material thereof, saidsurface of the steel material in the fuel reformer vessel is under anoxidative atmosphere by water vapor; manufacturing the vessel for thefuel reformer vessel using said raw steel material on which said Croxide layer is thus formed thereon; and filling thus manufactured vesselwith a reforming catalyst thereby to produce the fuel reformer vessel.10. A method of manufacturing a fuel reformer vessel for forming ahydrocarbon base fuel and water into a hydrogen rich gas, the fuelreformer vessel comprising a reformer catalyst filled portion, saidmethod comprising the steps of: forming a thin film containing Cr in ahigher concentration than that of a base material thereof on at least apart of a surface of raw steel material, said surface of the steelmaterial is under an oxidative atmosphere by water vapor; thereafterforming a Cr oxide layer on the surface of said raw steel material byheat treating said raw steel material under an oxidizing atmosphere of350 to 650° C. to convert Cr to Cr oxide; manufacturing the fuelreformer vessel by using said raw steel material on which said Cr oxidelayer is thus formed; and filling thus manufactured vessel with areforming catalyst thereby to produce the fuel reformer vessel.
 11. Themethod of manufacturing a fuel reformer vessel of any one of claims 7 to10, wherein an average thickness of said Cr oxide layer is 5 to 100 μm.